Proper way to try-catch a semaphore

Question

What is the proper way to wrap semaphore actions in a try-catch block? What happens if the acquire action is interrupted after it has acquired some number, but not all, of

Answer 1

The Semaphore.acquire(int) method is an all or nothing operation, either you get all the permits requested or you block. You can use a double try around your code, or let the (possible) interrupted exception from acquiring bubble up your call stack.

Double try block:

try {
    lock.acquire(permits);

    try {
        // do some stuff here
    } finally {
        lock.release(permits);
    }
} catch(final InterruptedException ie) {
    // handle acquire failure here
}

Bubble 'acquisition' exception:

lock.acquire(permits);

try {
    // do some stuff here
} finally {
    lock.release(permits);
}

On a tangent, do keep in mind that semaphores must be kept balanced by strict programming convention, so you should always release as many permits as you acquired.